A radio access network (RAN) refers to a network between mobile devices or mobile stations, such as mobile phones, personal digital assistants (PDAs), laptops, or any user equipment, and a core network. In traditional wireless macro-cell networks and mobile macro-cell networks, an area may be divided geographically into a plurality of cells and cell sectors, each served by a wireless base station communicating with a core network. The part of the RAN between the wireless base stations and the core network is referred to as the wireless backhaul. As the demand for high-speed wireless communications continues to increase, reaching the limits of macro cells in terms of the number of locations and penetration capability in indoor or densely-populated areas, research and industry are moving towards small-cell deployments with denser and smaller cells in future wireless access networks.
Wireless fronthaul or mobile fronthaul is an emerging network segment that enables a cloud-RAN (C-RAN) architecture suitable for small-cell deployments. In a C-RAN architecture, the digital baseband (BB) processing that is typically performed at wireless base stations located at remote cell sites is relocated to centralized baseband units (BBUs) located at a central site near a central office (CO) or a core network. As such, the wireless base stations located at the remote cell sites are replaced by remote radio units (RRUs) that interface with antennas for wireless radio frequency (RF) transmissions and receptions without the digital BB processing. Wireless fronthaul refers to the part of the RAN between the RRUs and the BBUs. By relocating the digital BB processing to the centralized BBUs, the C-RAN architecture may enable resource sharing and coordinated multipoint (CoMP) processing, such as joint signal processing, joint interference mitigation, and/or joint scheduling among multiple cells, and thus may improve network performance and efficiency.
Wireless fronthaul may be enabled by optical fiber communication technologies, where optical fiber links are employed for transporting signals between the RRUs located at the remote cell sites and the BBUs located at the central site. Some advantages of optical fiber transmission include low power loss, low latency, and high bandwidths (BWs). However, the employment of optical fibers and optical hardware add cost to the wireless fronthaul network. Thus, efficient usage of optical fiber links and optical hardware are important in wireless fronthaul design.